1. Technical Field
The present invention relates in general to metal-semiconductor interfaces and, in particular, to an improved system, method, and apparatus for making ohmic contact to silicon structures, such as silicon magnetic recording sliders, with low thermal loads and localized processing.
2. Description of the Related Art
In hard disk drives, magnetic recording heads are normally built upon a ceramic substrate on which an air bearing is formed so that the head can be flown over a disk surface. This ceramic substrate is called the slider body. The slider body is bonded by means of an adhesive layer to a stainless steel suspension which is then mounted on an actuator to enable the recording head to access all points on the disk recording surface. It is necessary to have a conductive path from the slider through the suspension to ground in order to avoid excessive tribocharging of the slider body. The ceramic substrate normally used for magnetic recording heads is sufficiently conductive that this requirement can be met by using a conductive adhesive for bonding the slider body to the conductive suspension.
Recently, there has been interest in using silicon for the slider body. This material presents a problem for establishing a conductive path to ground since an asymmetric conducting Schottky barrier is normally formed at a metal-semiconductor interface. Broadly speaking, the Schottky barriers have relatively low resistance for one polarity of voltage but a relatively high resistance for the opposite polarity of voltage, and the resistance is a nonlinear function of voltage for both polarities. This barrier may be overcome by providing an “ohmic contact.” An ideal ohmic contact has a resistance that is independent of voltage.
Special procedures must be used to achieve good ohmic contact between silicon and a metal. See, e.g., E. H. Rhoderick, Metal-Semiconductor Contacts, Oxford University Press, 1978. Typically, such procedures involve depositing an appropriate metal layer or layers on a silicon surface that has the native oxide layer removed. The workpiece is then annealed in an oven at elevated temperatures (e.g., 500° C. for 10 minutes). Unfortunately, subjecting the entire device to high temperature processing of this magnitude would destroy the sensitive magnetic recording heads in slider bodies. Thus, another solution for improving interfaces between metals and semiconductors in slider bodies would be desirable.